The invention concerns a hearing aid device or hearing device system, as well as a method to operate a hearing aid device or hearing device system, with at least one input transducer to acquire an input signal and transduce it into an electrical signal, an A/D converter to convert the electrical input signal into a digital signal, a digital signal processing unit to process the digital signal, a clock generator to generate a clock signal to control the digital signal processing unit, an output transducer, and a transmitting and/or receiving unit for wireless signal transmission between the hearing aid device or hearing device system and a further device.
A modern hearing aid device offers the possibility for wireless signal transmission between the hearing aid device and a further device, for example, a further hearing aid device, a programmer device, or an external transmission and receiving device. To transmit and/or receive, the hearing aid device comprises a transmitting and/or receiving unit.
However, hearing device systems with a hearing aid device and a transmitting and/or receiving unit are also known in which the transmitting and/or receiving unit is fashioned as an independent modular unit, preferably fashioned external to the hearing aid device, that is detachably connected with the hearing aid device to transmit or, respectively, receive. The transmitting and/or receiving unit is then preferably attached to the hearing aid device and is electrically connected with it by via contacts and conductors. Yet, it is also possible that the transmitting and/or receiving unit is not directly attached to the hearing aid device, but rather is carried on the body or the clothing of a hearing device user as a separate device. The connection to the hearing aid device then exists only via electrical contacts and conductors.
The transmitting and/or receiving units of the appertaining devices are frequently fashioned as “FM systems”, such that the transmitted signal is frequency-modulated. However, a modulation of the transmitted signal is not necessarily required, and is also not limited to a frequency modulation.
A hearing device with a processor located removed from the hearing device is known from U.S. Pat. No. 5,721,783 which comprises a wireless connection between the hearing device and the processor.
A hearing device is known from German patent document no. DE 693 27 951 T2 in which, among other things, a digital noise signal is added to the microphone signal for comparison of acoustic feedbacks.
In modern hearing aid devices, the signal processing ensues digitally. To control the digital circuits necessary for this, a clock signal is required. The clock signal of a digital hearing aid device is, for the most part, not very stable. Oscillator quartzes to stabilize the clock generator can not be used, due to their size. Consequently, the clock frequency is slightly dependent on temperature and supply voltage. It is therefore only quasi-stable. Nevertheless, the clock signal can also be regarded in a hearing aid device for a period of consideration of a few minutes as a uniform, stable signal with constant period duration and pulse width.
Due to the clocked operation of the hearing aid device, an electromagnetic noise signal in time with this clock frequency outputs from the hearing aid device and in particular from a clocked output stage. Furthermore, noise signals also ensue in multiples of this clock signal, also called overtones or harmonics. The receiver unit of the hearing aid device or hearing device system might detect a signal caused by overtones although no real receiver signal is present for the receiver unit. The frequency band in which the receiver signal lies is normally selected such that no harmonics of the clock frequency ensue within it. A slowly drifting clock frequency of the clock generator can then lead thereto that harmonics of the clock frequency lie within the frequency band of the receiver signal. The reception by the receiver unit is thereby disrupted.
Previously, it was widely, inadequately tried via elaborate filter stages to eliminate or, respectively, to localize in the hearing aid device narrow-band noise components already existing in the hearing device, that in particular extend into the frequency range of some 100 MHz via the harmonic components of the output clock frequency. Nevertheless, a high-frequency emission is not completely prevented, which leads in part to disruptions in the operation of a receiver unit. Furthermore, suitable shielding measures at the hearing aid device result in a remedy with regard to this high-frequency emission. However, all cited measures are very elaborate and expensive.